Protein markers and seed size variation in common bean segregating populations

18 páginas, 7 tablas.Selection and random genetic drift are the two main forces affecting allele frequencies in common bean breeding programs. Therefore, knowledge on allele frequency changes attributable to these forces is of fundamental importance for breeders. The changes in frequencies of alleles of biochemical markers were examined in F2 to F7 populations derived from crosses between cultivated Mesoamerican and Andean common bean accessions (Phaseolus vulgaris L.). Biochemical markers included the seed proteins phaseolin, lectin and other seed polypeptides, and six isozymes. The Schaffer’s test detected a high significant linear trend of the 63% of the polymorphic loci studied, meaning that directional selection was acting on those loci. Associations between seed size traits, phaseolin seed-storage protein and isozyme markers were detected based on the comparisons of the progeny genotypic means. In the interracial populations the intermediate form PhaH/T, b6, and Rbcs 98 alleles had a positive effect on seed size. In the inter-gene pool populations, a higher transmission of Mesoamerican alleles in all loci was showed, although the Andean alleles PhaT, Skdh 100 , Rbcs 98 , and Diap 100 showed positive effects on seed weight. Our results suggest that phaseolin and other seed proteins markers are linked to loci affecting seed size. These markers have good potential for improving the results of the selection and should be considered as a strategy for germplasm enhancement and to avoid the reduced performance of the inter-gene pool populations.Research was supported by the projects AGF97-0324 and AGL2005-01268/AGR from the Spanish Government, PGIDIT02RAG40301PR from the Galician Government (Spain), and EU-FEDER Funds. A. M. González thanks her fellowship to Ministry of Education, Culture and Sports of Spain. M. De la Fuente is grateful to the Xunta de Galicia for awarding her a fellowship grant.Peer reviewe